Pulp product and process of making the same



Patented Apr. 29, 1930 umrsa STATES- PATENT OFFICE ROBERT B. ARNOLD, OF RICHMOND, VIRGINIA, .AND RALPH M, HIXON, OF AMES, IOWA, ASSIGNORS TO TOBACCO BY-PRODUCTS 8t CHEMICAL CORPORATION, OF LOUISVILLE, KENTUCKY, A CORPORATION OF DELAWARE PULP PRODUCT AND PROCESS OF MAKING THE SAME No Drawing.

This invention relates to a slow-burning pulp product and to a process for producing the same.

It has been common in the art heretofore to 5 produce pulp products, such as coarse papers, pasteboards, and so-called lumber-substitutes, such as building boards or plaster-boards and sheathing material, from various plant materials by processes generally involving rather drastic treatment of the material either with chemicals or long continued mechanical action, such as beating, for the purpose of setting free the natural fibers of the plant'material, the resultant pulp product consisting 5 chiefly of a mass of matter normal cellulose fibers. In such processes practically all the plant material exce t the normal cellulose fibers, is removed. roducts of this nature must, as a matter of economy, be made from plants which contain a relatively large amount of normal cellulose fiber and which at the same'time must be relatively low in cost. Thus, there is a restriction as to the plant maerial which can be employed, and a relatively low output of finished product compared with the amount of starting material employed. Furthermore, such products are combustible to such an extent that if once ignited they generally continue to burn, for example, like punk, that is to say, in most cases the fire does not die out of itself.

One object of the presentinvention is to provide a process which will employ tobacco plant material as-the starting material and which will utilize practically all of the plant material except that portion which is relatively easily soluble in water, whereby the percentage of finished product from a given amount of starting material is greatly increased as compared with prior processes. I

A further object of the invention is to provide a pulp product and particularly a lumber-substitute which, if ignited, will burn so poorly that the fire dies out in a relatively short time.

In carrying out the process, the tobacco plant material is first subjected to an operation by which the nicotine is removed and recovered and simultaneously, or successively,

or both. the constituents easily soluble in wa- Application filed November 12, 1927. Serial No. 232,944.

ter are removed, this including all nitrates or nitric acid combinations. An important characteristic ingredient of tobacco is nitrate of potassium, and this is relatively easilysoluble in water and therefore can be removed without difliculty from the plantmaterial. The removal of this ingredient and the retention of other less soluble or insoluble mineral salts in the final productvmay be the cause of the relatively incombustible nature of such final product.

After the removal of all those ingredients which are easily soluble in water by steps which avoid any drastic chemical treatment, the plant material thus obtained is submitted to a mechanical treatment whereby it is shredded, that is to say split, cut or torn into small strips, strands or threads in the nature of manufactured or artificial fibers ofrelatively large size as compared with the natural fibers of vthe plant. Any normal cellulose or similar natural fibers will be found in the strips, strands, of threads, care being taken not to carry the shredding or cutting operation to the point of feeding the individual natural fibers. The normal cellulose fibers in tobacco stems are apparently of a springy nature, which may be due to the fact that the individual fibers, or at least many of them, seem to be helically coiled. Hencethe products made from tobacco stem pulp by the present process has considerable elasticity and tensile strength. i

The. shredding, cutting oratearing, of the extracted tobacco plant material is best done by a hollander or a beating engine such as is used in paper manufacturing, but in this case the beater must be so adjusted as to give a relatively coarse strand and the beating operation must not be carried out to too great an extent, because if it is, a large proportion of the plant material which is diflicultly soluble in water will be dissolved by long continued beating in Water and will be ost.

After the extracted plant material has been formed into strips, strands or threads the material in its wet condition is suitably conipacted to a matted mass, as, for example, by running it onto a screen or a continuous filter,

from which it may be removed as a layer or sheet.

Where such a layer or sheet is pressed as for example either in a hydraulic press, or by pressure rolls, as where the layer is made as a web in a continuous process, the resultant product when dried will be found to have shrunk to a great extent and to be very hard and dense. While such a roduct is useful, it is not the best where the nal product is to have relatively high heat insulating properties or where considerable tensile strength is required, as for example in a lumber-substitute. Therefore, the best product is obtained .by first drying the layer or sheet of pulp as it comes from the continuous filter or from the screen and then using this shrunken, dried pulp either alone or admixed with other fibrous materials as a new starting material for the manufacture of the final sheets, webs or boards. The shrunken, dried pulp above referred to seems to have acquired some new properties in that when again placed in a beating engine with water and subjected to further beating until once more in the form of wet pulp, this pulp when formed into layers or sheets and then pressed and dried will not shrink to any great extent as did the original pulp. Furthermore, the second beating operation does not cause any appreciable loss of material, which would indicate that the first drying step had resulted'in changing some of the slightly water-soluble material in the first pulp into practically insoluble material. In any event the result is that by two beating op erations with interpolated forming and drying steps, a final pulp is obtained which may be formed into a web, layer or sheet on a screen or continuous filter, then pressed, but not too much, and then dried to form a sheet product of excellent heat insulating properties and very satisfactory as a lumber substitute.

If the layers, webs, or sheets of formed pulp be pressed to such an extent as to remove all the free water, the resultant product when dried will be too dense and therefore not as good a thermal insulator as where it is more porous, the insulating properties depending chiefiy on the presence of air particles well distributed through the material.

Hence in practice it is best to carry the pressing to the point where 65 to 75 per cent (by weight) of water remains in the board or sheet. Thereupon the product may be dried in the usual manner and will be found to be entirely satisfactory in insulating properties.

There may be combined with the tobacco plant pulp, a lesser amount of pulp made from other materials with some benefit to the resulting product. For example, where a strong building board is desired it has been found that an addition of pieces of old burlap to the tobacco plant material in the beating engine, and the beating of the two products to a resultant mixture of pulps gives a pulp material which when made into sheets or boards and dried is very satisfactory on account of its tensile strength and the shrinkage during drying is greatly reduced.

Instead of beating together the tobacco plant material and the old burlap to produce a pulp mixture, it is advisable to prepare the two pulps separately and then combine them in a beating engine. In this way the tobacco plant pulp may be produced by the process hereinbefore described in which the pulp is made, formed on the screen or filter, then dried and then put in water and again beaten to pulp. By employing this method there may be combined with the dried pulp, old

newspaper pulp, kraft pulp, or wood-wool or excelsior. In using excelsior some saw dust may be added. In every case, however, the tobacco plant pulp must form the larger part of the resultant product, or the fire-resisting properties may be lost.

One specific method which gives satisfactory results is to take tobacco stems as usually received in pieces from 4 inch to three inches long, which are then wet down or ordered with water using an amount of water sufficient to thoroughly wet the stems. Usually this requires an amount of water varying from one half the weight of the stems up to about an equal weightf The stems are allowed to stand fora short time, usually half hour to two hours, to allow the moisture to thoroughly penetrate the stems. The moistened stems are then extracted with water, warm water being preferable, in any suitable manner,-as for instance in a continuous diffusion battery of the type used in the extraction'of sugar from beet chips,until practically all of the nicotine compounds and also all other ingredients which are readily soluble in water have been dissolved out of the stems. The liquid extract is removed from the stems and treated to recover the nicotine by any desired process, as for example, theusual distillation processes.

The extracted stems are then put into a beater or hollander of any usual type, with sufficient water to permit agood beating acening of the slightly soluble pentosans, which tends to cement abutting strips, or strands, and thereby adds to the tensile strength of the material.

The pulp produced in the beater is formed into sheets or a continuous web of the proper thickness and density by operations analogous to those used in paper making. For example, the pulp may be run onto a traveling screen so that the pulp is formed into a continuous web of matted shredded material, the web then passing between pressure rollers which consolidate the web to the proper extent. It is important to have the material compacted a reasonable amount, but not too much, the obect being to have well-distributed air pockets throughout the product, thereby making the product a good heat insulator, which would not be the case if the material were pressed to such an extent as to make the product hard and dense.

On the other hand if the matted material is not pressed enough, too much water will be left in it, making the drying cost excessive. Sufficient pressure to result in a product containing from twenty-five to thirty-five per cent of dry material, depending upon the density desired in the dry product, has been found to be satisfactory. After pressing, the sheets may be cut to length and dried in a suitable dryer. The dried pieces or boards are trimmed to exact size and are ready for use.

Where it is desired to size the material, for example, to water-proof it, the size is added to the pulp. \Vhile Various ingredients may be used for sizing, it has been found that the ordinary rosin sizes, or rosin and silicate of soda are satisfactory. After the size has been properly incorporated with the pulp, which may be done by adding it to the Water in the beater, or in a separate mixing machine, the size is precipitated on the filaments by the addition of alum or other suitable reagent. This precipitate is intended to form a coating on each individual fiber. Vhere, however, only the outer surfaces of the product need be water-proofed the rosin size may be ap Jlied to one or both surfaces of the web or s eet, by brushes, by a spray or by size-applying rollers feeding the size from a suitable fount. Thereafter an alum solution or the like may be similarly applied.

Where it is desired to form a board with a smooth finish, for example, a plaster finish, powdered gypsum may be applied to, say, one surface of the board after it.leaves the pressure rolls, the gypsum being sprinkled on the surface by a suitable device, whereupon the web or board is passed between pressure rollers to force the powdered gypsum into the surface of the board. The finished boards or sheets comprise chiefly a compressed matted mass of shredded, extracted tobacco plant material, the principal ingredient ofthe respective strands or threads being the constituents, other than normal cellulose, which are not readily soluble in water. In general the constituents known chemically as pentosans, .and comprised under the formula C H O form a large part of the product. As the water leaves this material, the latter in drying passes through a sticky or adhesive stage, the adhesive, when sufficient water has been removed, taking a solid non-adhesive form.

It has been found that, in the process of drying, the compressed matted sheet shrinks to a considerable extent and hence the product is too dense for some uses. If,"however, the shredded material is first dried, which may be done without pressing it into a sheet, and this dried material is used in the proportion of about sixty percent dried pulp to forty per cent of original-that is newly made pulp in forming the compressed sheet, the shrinkage on drying is largely overcome and a board of lowdensity is obtained. The same effect may be produced by mixing twenty percent to thirty percent of saw dust or exploded or shredded wood with the original pulp. Such materials as straw or peanut hulls may be used to replace saw dust to some extent if desirable. Also, other pulp materials may be combined with the original pulp.

There the resulting product is to be used as a buildingmaterial such as a coarse sheathing paper or more particularly a lumber substitute or building board, highly satisfactory results have been obtainedby combining pulp made from extracted tobacco plant material with other material in the proportions of about to 80% of the former and 45% to 20% of the latter. For example, the following combinations have been found to be good for the purposes named:

80% original pulp from extracted tobacco plant material, 20% pulp from old burlap. A building board inch thick made from this material weighed about 0.8 pounds per square foot.

80% dried pulp from extracted tobacco plant material, 10% news pulp and 10% kraft pulp gave a board weighing about 0.77 pounds per square foot.

55% original pulp from extracted tobacco plant material, 5% kraft pulp, 20% excelsior, 20% sawdust, gave a board weighing 0.65 pounds per square foot. I

original pulp from tobacco plant ma terial, 25% sawdust and 10% old news pulp. The board made from this weighed 0.83 pounds per square foot.

For a strong and heavy board which can be used for other purposes than as a building board, for example as an artificial lumber 9 material was principally extracted tobacco stems. All the samples were inch thick.

What we claim is: In a process of making a pulp product from tobacco waste material, the steps which comprise extracting nicotine from said material and also removing from it all other constituents which are readily soluble in water, then mechanically reducing the extracted tobacco plant material to a mass of matted strips, drying said matted mass, the beating said dried mass in water, together with other materials to produce a pulp, using said pulp to form a sheet and drying the sheet.

In witness whereof, we have hereunto set our hands.

ROBERT B. ARNOLD. RALPH M. HIXON. 

